- Libraries - Haskell.org

#4189: Add (<.>) operator (generalizing (.) to Functor)
by Maciej Marcin Piechotka 06 Aug '10

06 Aug '10

The proposal is to add (<.>) function to Data.Functor/Control.Applicative: (<.>) :: (b -> c) -> (a -> f b) -> a -> f c f <.> g = fmap f . g -- (<.>) = (.) . fmap In intend it is related to <$> in the same way as (.) is related to $: (a . b . c) d = a $ b $ c $ d (a <.> b <.> c) d = a <$> b <$> c <$> d a is not specialized to f a to allow such chaining: const 1 <.> print <=< (read :: String -> Int) <.> readFile :: (Num t) => FilePath -> IO t Discussion deadline: 31th August 2010

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Bug in Data.Map
by Daniel Peebles 05 Aug '10

05 Aug '10

Hi all! Taylor Campbell found a bug in Data.Map but wasn't able to post to this mailing list so I'm submitting this on his behalf. ---------------------------- Deletion in Data.Map does not always preserve the balance of a tree. Deletion in Data.Set appears to preserve the balance in some cases where Data.Map does not; I don't know whether Data.Set always leaves the tree balanced. I have attached two files to test the balance of trees after a random sequence of insertions and a pathological sequence of deletions (deleteMin -- although this is not pathological for some applications such as priority queues). TestMap.hs reliably demonstrates for me that deleteMin readily yields an unbalanced tree, if I supply a size of 10000 to test_map. TestSet.hs does not. The salient difference between Data.Set and Data.Map, I believe, is the choice of delta (w in Adams' paper), which is 4 in Data.Set and 5 in Data.Map. Since Adams' paper claims that when alpha (i.e. 1/ratio) is 1/2, w must exceed about 4.646, this seems suspect. But I haven't analyzed the reasoning in Adams' paper to find whether his conclusions are wrong. What I do know is that I can break trees when w is 5, but I have not been able to break them when w is 4. I also noticed a comment in Set.hs saying that a value of 4 for w improved performance on many operations. I have also not been able to break trees if I change deletion to use join rather than balance. But that slows everything down a good deal more, I believe, than simply changing w from 5 to 4.

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xhtml maintainership?
by Ganesh Sittampalam 03 Aug '10

03 Aug '10

Hi, I believe the xhtml package is currently unmaintained. As it is something that used to be distributed with GHC, is it something that libraries@ could/should take on? Cheers, Ganesh

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Proposal: Make Permissions type abstract
by Ian Lynagh 03 Aug '10

03 Aug '10

Hi all, Proposal: Make Permissions type abstract Ticket: http://hackage.haskell.org/trac/ghc/ticket/4149 The Permissions type in System.Directory aims to be a lowest-common-denominator type. This makes it unsuitable for some tasks. For example, a copyPermissions primitive had to be implemented, as it is not possible to use the getPermissions and setPermissions functions to copy the permissions from one file to another: $ ls -l foo* -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo1 ---------- 1 ian ian 0 Jun 23 21:27 foo2 ---------- 1 ian ian 0 Jun 23 21:27 foo3 $ hd -e 'System.Directory.copyPermissions "foo1" "foo2"' $ hd -e 'System.Directory.getPermissions "foo1" >>= System.Directory.setPermissions "foo3"' $ ls -l foo* -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo1 -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo2 -rwx------ 1 ian ian 0 Jun 23 21:27 foo3 I think we would be better served by the Permissions type being abstract in System.Directory, with the unix and Win32 packages providing the real definition, and some system-specific functions on it. This would allow the generic get/set functions to implement copyPermissions. This proposal just does the step which has most potential to cause problems for packages that use the type: It makes the type abstract in System.Directory (and adds explicit setter functions, so no functionality is lost). (patch is in the ticket) The type is also exported in Haskell 98's Directory module. I think this should get its own copy of the type. Suggested discussion deadline: 9 July 2010. Thanks Ian

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Error in Haddock documentation for process
by Ivan Lazar Miljenovic 30 Jul '10

30 Jul '10

I just spotted the following problem in the documentation for readProcess [1]. The documentation has the sample usage returning an "IO (Either a String)" action, yet the function only returns an "IO String". > readProcess "date" [] [] Right "Thu Feb 7 10:03:39 PST 2008\n" [1]: http://hackage.haskell.org/packages/archive/process/1.0.1.3/doc/html/System… -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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ANN: weighted-regexp-0.1.0.0
by Sebastian Fischer 28 Jul '10

28 Jul '10

Hello, this year's ICFP features A Play on Regular Expressions where two Haskell programmers and an automata theory guru develop an efficient purely functional algorithm for matching regular expressions. A Haskell library based on their ideas is now available from Hackage. For more information (and a link to the play) visit: http://sebfisch.github.com/haskell-regexp/ Cheers, Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)

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HTTP-4000.0.9
by Christian Maeder 28 Jul '10

28 Jul '10

Hi all, did someone hear from Sigbjorn, recently? I'm worried about the the maintainer of http://hackage.haskell.org/package/HTTP The issue tracker is terribly full of spam: http://trac.haskell.org/http/report/1 Cheers Christian -- original message Hi Sigbjorn, Under x86 solaris the attached example with simpleHTTP no longer works. The request blocks. It works with HTTP-4000.0.8! And it works under linux with HTTP-4000.0.9! What changed? Do you have an explanation? Thanks Christian <soapenv:Envelope encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"><soapenv:Body><ProveTPTPProblem><in0>%-------------------------------------------------------------------------- % File : No information % Domain : No information % Problem : asym.dfg % Version : No information % English : No information % Refs : No information % Source : No information % Name : [soapTest] % Status : unknown % Rating : ? % Syntax : No information % Comments : File generated by dfg2tptp Version 0.47a %-------------------------------------------------------------------------- fof('ga_non_empty_sort_Elem',axiom,( ? [U] : ssElem(U))). fof('trans',axiom,( ! [U,V,W] : ((ssElem(U) & ssElem(V) & ssElem(W)) => ((ssTilde__(U,V) & ssTilde__(V,W)) => ssTilde__(U,W))))). fof('irrefl',axiom,( ! [U] : (ssElem(U) => ~(ssTilde__(U,U))))). fof('asym',conjecture,( ! [U,V] : ((ssElem(U) & ssElem(V)) => (ssTilde__(V,U) => ~(ssTilde__(U,V)))))). %-------------------------------------------------------------------------- </in0><in1>10</in1></ProveTPTPProblem></soapenv:Body></soapenv:Envelope>

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can I indicate that an old version is not to be used, and some more questions
by S. Doaitse Swierstra 28 Jul '10

28 Jul '10

I uploaded a version of the uu-parsinglib to hackage. Only later I discovered that it depended on a verion of base >= 4.2, whereas I indicate > 4 in my .cabal file. I repaired this by uploading a new version in which only the cabal file has changed. This raises the following questions: - the Haskell code did not change, but I still had to bump the version number? - can I remove the incorrect version or indicate that it is superseded by the new version? - since I do not have a wide variety of Haskell installations and package versions on my machine, it would be very nice if the hackage server could test a package against the extremes of the indicated dependency ranges before installing. This would have prevented the mistake I made (and which undoubtedly others will make too) Doaitse

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Re: Bad behavior in haskell-regex-tdfa version 1.1.3
by Chris Kuklewicz 26 Jul '10

26 Jul '10

Version 1.1.3 of regex-tdfa has a bad bug. The error was something I changed from 1.1.2 to 1.1.3 that was simply Wrong. It would only trigger at the 100th character, however. The Wrong thing has been reverted. It should be Right again. The new version on hackage and in darcs is 1.1.4. Cheers, Chris Kuklewicz On 21/07/2010 14:01, David Fox wrote: > On Mon, Jul 19, 2010 at 1:22 PM, Joachim Breitner <nomeata(a)debian.org > <mailto:nomeata@debian.org>> wrote: > > Hi David, > > Am Montag, den 19.07.2010, 11:26 +0100 schrieb David Fox: > > I'm getting errors like this from version 1.1.3 of haskell-regex-tdfa > > which is now in sid: > > > > Explict error in module Text.Regex.TDFA.NewDFA : compressOrbit,1 > > > > reverting to 1.1.2 fixes it. Also, the homepage and the darcs repo > > given in the cabal file appear to be out of date. > > > > hmm, not good. Do you have a minimal test case? > > > ...I was hoping you wouldn't say that. Lets see ... ok, attached. >

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Re: Cross platform file manipulations
by Henning Thielemann 26 Jul '10

26 Jul '10

On Mon, 26 Jul 2010, Kazu Yamamoto (山本和彦) wrote: > Hello, > > Thank you for your reply. > >> I think it is intended to have OS specific paths in FilePath values and >> operate on them with OS specific functions as provided by the 'filepath' >> package. Sure, an abstract FilePath type would be nice and was discussed >> from time to time, but did get reality so far. > > OK. Sorry, I wanted to write 'but _not_ did get reality so far'.

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